1. Field of the Invention
The present invention relates to a method and apparatus for controlling a two-stage valve.
2. Description of the Prior Art
It is known that when two-stage valves are controlled by traditional techniques the dynamic response of the main stage spool is dependent on the pressure supplied to the pilot stage. This undesirable dependency arises because the flow gain of the pilot stage is approximately proportional to the pilot pressure. One prior solution to this problem is to introduce a pressure regulator between the pilot and main stage valves to maintain a constant pilot stage supply pressure irrespective of the pressure in the rest of the hydraulic system.
It is an object of the present invention to provide a control system for a two-stage valve which is capable of controlling the valve in such a manner that its dynamic response is independent of the pressure supplied to the pilot stage thereof, while avoiding the use of a dedicated pressure regulator, as described in relation to the prior art.